RESEARCH GOALS: The project has for its goal (1) the experimental verification of several phenomena predicted by previous thermodynamic arguments to occur in monolayers at fluid interfaces when electric fields are applied normal to the interface, and (2) to extend the arguments to biological and bilayer membranes. These effects are (a) substantial displacement of molecules into or out of a field when the monolayer is at a first-order phase transition, (b) a field-induced surface pressure change in insoluble monolayers, (c) the change of adsorption with soluble monolayers, (d) alterations in isotherm shapes at higher-order phase transitions, and (e) the change of composition caused by a field acting on a multicomponent monolayer. The first two effects have been demonstrated quantitatively. Preliminary results on the last three are not yet conclusive. The thermodynamic treatment of field effects on model membranes has been developed, suggesting new experiments and giving further insights into biomembrane polarization. The work will assist quantification of the mechanical, compositional and conformational aspects of the effects of fields on biomembranes.